The Milwaukee Marine and Freshwater Biomedical Core Center is an extramural center of the National Institute of Environmental Health Sciences (NIEHS). It is a support organization for mechanistic studies using aquatic organisms that examine human environmental health issues. It has the general objectives 1) to increase understanding of environmental health problems using aquatic models, 2) to attract scientists to the Core Center from the immediate region and around the country and to foster interactions among member investigators, and 3) to support training for students and professionals in the area of environmental health. These goals are addressed by three units in the Core Center, each with specific aims to realize the programmatic objectives. For the Administrative Core: to support relevant, high quality research; to support feasibility projects: to recruit new investigators; to build research strength through collaborative interactions among members, through seminars, by encouraging new research initiatives, and providing travel to gain expertise; to support training with student support, efforts to draw minorities into the Core Center, and to make Core Center facilities open to students; and to work to obtain a Marine Biomedical Center. For the Facilities Core: to enhance the instrumentation; to stimulate staff development; and to pursue construction of new physical facility for Marine Biomedical Center. For the Research Core: to carry out mechanistic studies with aquatic organisms of importance for the understanding of human environmental health; and to work on research requested by NIEHS. Research utilizing the Core Center focuses on a number of human environmental health problems including target organ specificity of pyrethroid insecticides, regulation of cytochrome p-450 expression, mechanism of action of 2,3,7,8-tetrachlorodibenzo-p-dioxin, possible role of Zn finger proteins in DNA damage caused by heavy metals, the role of cellular metals in oxidative stress, selective roles of the metal clusters in the heavy metal binding protein metallothionein, neurobehavioral effects of lead, an anuran model for examining the impact of low level exposure to toxic substances on development, effects of Pb on intact neuronal circuitry, immunohistochemical studies of metallothionein induction after exposure to cadmium. Studies involving aquatic biomedical models development include examination of the mechanism of insulin action, glucocorticoid receptor regulation, genetic transposition and the transport properties of turtle bladder.